I can't understand this joke! What do you mean? Please explain!

1, the waiter should be a waiter. It was said before that this classmate refused to admit that "taxi" means taxi. He called him wrong, and the waiter obviously thought he was calling him because of his poor English, and made a joke.

2, this is easy to understand, the doctor's English is "doctor", this classmate studies English very hard, so that when asked what his doctor said, he blurted out English reflexively.